Environmental factors, light temperature

The stability of a drug in vitro may be adversely affected by various environmental factors including temperature, pressure, light, moisture and pH. 

Chemical stability under a variety of macro- and microenvironmental conditions is a highly critical property determining the expected shelf life of products. The stability of the bulk solid and in solution must be studied, whereby the influence of environmental factors (pH, temperature, humidity, oxygen, light) and including the presence of various excipients on drug stability must be established. 

All the environmental factors, light, water, macro- and micronutrients, pH of the soil, temperature, and probably others have still been insufficiently investigated. There was considerable interest in this type of research in the 19th century mostly the alkaloids were isolated as salts of silicotungstic or phosphomolybdic acids. Because these form different complex salts with alkaloids encountered in the plant, it must be assumed ipso facto that the obtained data were only crude approximations. 

The possible effects of increased atmospheric CO2 on photosynthesis are reviewed by Goud-riaan and Ajtay (1979) and Rosenberg (1981). Increasing CO2 in a controlled environment (i.e., greenhouse) increases the assimilation rate of some plants, however, the anthropogenic fertilization of the atmosphere with CO2 is probably unable to induce much of this effect since most plants in natural ecosystems are growth limited by other environmental factors, notably light, temperature, water, and nutrients. 

The purpose of stability testing is to assess the effects of temperature, humidity, light, and other environmental factors on the quality of a drug substance or product. The data produced are used to establish storage conditions, retest periods, shelf loss, and to justify overages included in products for stability reasons. The most useful equation relating temperature and reaction rate is the Arrhenius equation. This equation (27) may be integrated and rewritten as Eqs. (31) and (32). 

C02 is not the only factor involved in photosynthesis, so that for its use, other factors must be at levels that do not limit the process. Light, temperature, amount of available nutrients and the relative humidity are other environmental factors affecting photosynthetic activity. 

In general, unless a local reservoir (i.e., intermediate host that may or may not be affected by the virus) is established, pathogens are easily killed by unfavorable environmental factors such as fluctuations in temperature, humidity, food sources, or ultraviolet light. For this reason, their persistency is generally limited to days. However, freeze-dried pathogens can remain in a preserved state almost indefinitely and are reactivated when exposed to moisture. 

Numerous nitrogen-free toxins occur in plants. As discussed in the introduction to this Chapter, many of these compounds are believed to be for the protection of the plant from herbivory. However, because there is such a diversity in plant compounds, there are other functions they serve, e.g., insect attractants for pollination, and protection against environmental factors, such as UV light, low or high temperatures, drought, etc. 

Alteration of environmental factors (e.g., lighting, noise, temperature)... 

All the work described in this section thus has a common theme inasmuch as it deals with the influence of various environmental factors on the activity of homogeneous oxidation catalysts. In particular, the results shed valuable light on the ways in which temperature, the structure of the organic substrate, the concentration and the form of the catalyst, and reaction time may all affect the nature and kinetics of the various competing stages involved in the reaction of organic compounds with molecular oxygen. 

The other major class consists of environmental factors. Among these are ambient atmosphere conditions of temperature, pressure, and humidity, as well as composition of the atmosphere, including the presence of atmospheric pollutants, such as ozone or carbon monoxide. Light and noise and the patterns in which they occur are important. Social and housing (caging) conditions may also influence response of subjects to a toxicant. 

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